lc297.二叉树的序列化与反序列化

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Codec:

    def serialize(self, root):
        """Encodes a tree to a single string.
        
        :type root: TreeNode
        :rtype: str
        """
        res = []
        def dfs(root):
            if not root:
                res.append("$")
                return 
            res.append(root.val)
            dfs(root.left)
            dfs(root.right)
        dfs(root)
        return res

        
    def deserialize(self, data):
        """Decodes your encoded data to tree.
        
        :type data: str
        :rtype: TreeNode
        """
        l = data[::-1]
        def construct(val):
            if val != "$":
                node = TreeNode(val)
                node.left = construct(l.pop())
                node.right = construct(l.pop())
                return node
            else:
                node = None
        return construct(l.pop())
        

# Your Codec object will be instantiated and called as such:
# codec = Codec()
# codec.deserialize(codec.serialize(root))